Mastering the third space: Innovations in intramural endoscopic surgery for gastrointestinal disorders

Table 1 Key differences of peroral endoscopic myotomy procedures

POEM type	Primary Indication	Target anatomy	Submucosal entry point	Myotomy site	Myotomy length
C-POEM	Cricopharyngeal bar/UES dysfunction	Upper esophageal sphincter (cricopharyngeal muscle)	2-3 cm proximal to the cricopharyngeal bar	Cricopharyngeal muscle	Approximately 2 cm
E-POEM	Esophageal achalasia	Esophageal body and LES	10-14 cm proximal to EGJ	Circular ± longitudinal layers of esophagus and LES	7-10 cm
G-POEM	Refractory gastroparesis	Pyloric sphincter	3-5 cm proximal to pylorus	Pyloric muscle ± distal antrum	2-3 cm
Z-POEM	Zenker’s diverticulum	Cricopharyngeal muscle and diverticular septum	3 cm proximal to septum or directly over it	Cricopharyngeal muscle and septum	Approximately 2 cm

All terms have been standardized; and time and distance units have been harmonized for consistency. POEM: Peroral endoscopic myotomy; C: Cricopharyngeal; E: Esophageal; G: Gastric; Z: Zenker.